The present invention relates to bread products having improved keeping qualities containing high levels of non-fat dry milk that substantially increase the quantity and quality of the bread's protein and calcium content. In particular, the present invention relates to bread products having improved keeping qualities, based upon grain flours having a wheat protein content of 17% to 30% and containing "low heat" non-fat dry milk in amounts that provide a composition capable of being formed into a bread product having an additive-free specific volume greater than about 4.0 cc/g.
Gluten is the primary result of the hydration of the proteins gliadin and glutenin by the addition of water to wheat flour, and is responsible for gas retention in yeast leavened baked goods. Gluten also furnishes the cellular network which characterizes the crumb structure of bread and similar yeast leavened baked goods. The volume of these baked goods, that is, the specific volume (cc/g)--or inverse density--, is a measure of lightness and is directly related to the gluten content of doughs made from flours of about 10% to 17% protein content.
For optimal effectiveness, gluten must also be fully developed, a process by which the cross-linked gluten molecules are more linearly aligned making the dough less stiff and elastic and more extensible. As a measure of this extensibility, the ideal dough can be stretched to a translucent membrane of uniform thickness. During the mixing stage of bread making, the wheat proteins in flour are not only hydrated, but the gluten thus formed is developed. In the "no-time" process, a straight dough method with both a shortened mixing time and a substantial reduction of the fermentation stage, gluten development is still accomplished by mechanical means, but with the assistance of reducing agents to break the disulfide bonding on the gluten protein to permit a more rapid realignment by the mixer. The mixing time for full gluten development is reduced to 10 to 15 minutes in the "no-time" method.
Wheat flour used in making white pan bread generally has a protein content between 11% and 13%. Vital gluten, usually as gluten flour with a vital gluten content of 75% or more, may be added to bread flour to increase the protein content. The amount of vital gluten which can be added while still maintaining workable doughs and acceptable breads is about 3-5% of the flour by weight. The addition of vital gluten to wheat flour results in changes in the dough and bread which are directly related to the added amount. These changes consist of the development of increasingly tough, rubbery doughs, difficult to develop into extensible ones and, after processing, breads with increasingly gluten-like characteristics such as an open irregular crumb with gluten strands separating crust and crumb and a rubbery texture of both crust and crumb.
The use of cellulosic filler to reduce the caloric content of bread has permitted the addition of vital gluten in amounts greater than 5%. The vital gluten restores the dough strength lost by flour dilution. This concept has resulted in a series of inventions. Singer, U.S. Pat. No. 3,547,634, describes a low calorie loaf containing less than 15% assimilable carbohydrate with dry ingredients made up of gluten flour (50 parts) and vegetable gum (1-10 parts). The invention specifies a gluten to fiber ratio of 5:1 to 1:1, a ratio far higher than taught in subsequent patents, which disclose that the high gluten content of the baked goods made following the Singer teachings would produce an unacceptably tough and chewy product.
Tsantir and Gorman, U.S. Pat. No. 3,767,423, disclose a composition for use in making a low calorie bread in which the wheat flour is diluted with rice and/or soy hulls up to 20 parts and gluten up to 10.6 parts per 10 parts of flour. The inventors devised an index of user acceptability which is inversely proportional to the wheat gluten content of the product.
Titcomb, U.S. Pat. No. 3,979,523, describes a reduced calorie loaf with 22-25 parts by weight of alpha-cellulose and 10 parts by weight of wheat gluten per 100 parts by weight of wheat flour. Titcomb, U.S. Pat. No. 4,590,076, subsequently disclosed that at least 70% of the alpha-cellulose particles pass a 200 mesh screen. Although the amount of alpha-cellulose dilution of the wheat flour was maintained at the 22-25% level specified in the earlier patent, the amount of wheat gluten was reduced to at least 5% of the flour or sufficient to substantially replace the protein lost in the flour by dilution with alpha-cellulose.
Thompson, U.S. Pat. No. 4,109,018, disclosed the quantitative relationship between alpha-cellulose and vital wheat gluten as well as the limits of these ingredients admixed with wheat flour to be similar to that disclosed by Titcomb. Thompson discloses a dough for making a bread product having 3-9 parts of vital wheat gluten and 10-20 parts of an alpha-cellulose flour per 100 parts of wheat flour. However, the Thompson invention further discloses the addition of 0.5-6.0 parts of a hydrophilic gum and 5-12 parts of an elastic protein material which reportedly increase the moisture content to about 43% in contrast to about 36% for conventional bread.
Patton et al., U.S. Pat. No. 4,587,126, discloses a reduced calorie bread using from 5-20% of citrus vesicle fibers per 100 lb of wheat flour having about 14% protein content. The protein content is achieved by the addition of gluten flour in the amount of 5% and oat flour in the amount of 15% based upon the weight of the flour. Although it was stated that the absence of bucky dough and tough crumb associated with gluten flour is attributed to the citus vesicle fibers, this can also be attributed to the oat flour, particularly because the gluten level of these flours in the Patton reference are at the upper level for flours used in making normal white pan bread.
Oomah, Cereal Chem., 60(3), 220-225, (1983), disclosed that as the concentration of oat flour increased from 5-25% in a composite wheat-oat flour combination, maximum torque decreased in the mixograph. Subsequently, Rudel, U.S. Pat. No. 4,961,937, disclosed that a composition of flours containing gluten flour in amounts sufficient to produce a vital gluten content of at least 17% of the dry mix and a milled oat groat product in amounts sufficient to produce a soluble oat dietary fiber content of flour 0.2% to 56.0% of the vital gluten content of the dry mix could be used to make baked products which are consumer acceptable and capable of being manufactured with existing methods and equipment.
The shortened fermentation time of the "no-time" process of less than one hour produces a bread with a much reduced or eliminated fermentation taste and aroma. The use of non-fat dry milk (NFDM) up to 8.2% but usually 2-3% based upon flour weight, sweeteners or flavors can be used to compensate in flavor but breads made by such short-cut methods still suffer from flavor deficiency. The "no-time" process products also suffer from a poorer shelf life which can be improved by the use of crumb softeners but still are not well accepted when shelf lives of one to three days are required.
These problems are not limited to the "no-time" process. The continuous mix process also suffers from the same limitations because of the lack of flavor development. Although continuous-mix bread has a fine grain and silky texture, it is very low on flavor because the flour and other ingredients have a reduced exposure time to yeast and the products of fermentation. However, the process is intolerant of NFDM, and the use of this flavor adjunct is therefore limited.
The traditional method of making bread, the sponge and dough process, has fermentation periods of four to over five hours. During this time there are products formed which impart a large part of the flavor to bread. NFDM added in amounts of 4-6% of the flour weight enhances the flavors of these natural fermentation products.
Conventionally, NFDM is heat-treated to denature certain of the milk proteins, particularly the whey proteins, lactalbumen and globulins. This "high heat" NFDM is considered essential for use in leavened baked goods because the undenatured proteins of "low heat" dried non-fat milk react unfavorably with gluten causing poor structure with reduced gas retention and, consequently, loaves of unacceptable volume.
Even "high heat" NFDM has limitations. Levels of "high heat" NFDM over 5% in the sponge and dough process have adverse effects on loaf volume. These negative effects are more pronounced in the "no-time" and continuous-mix processes; in the former, "high heat" NFDM use is recommended at the 2% level and in the latter, above the 1% level loaf structure is compromised. It should be noted that levels of "high heat" NFDM below 3%, based on flour weight have little effect on bread flavor. Efforts have been made to increase the level of "high heat" NFDM addition in the continuous-mix process.
Andt, U.S. Pat. No. 3,271,164, discloses a continuous process of bread making in which there is added to the dough about 4% of NFDM (high heat) and an additive consisting essentially of from about 0.1% to 0.9% karaya gum and from about 0.02% to about 0.1% of materials selected from algins and carrageenans, all percentages being by weight of the flour. Glabe and Jertson, U.S. Pat. No. 3,411,919, describe a continuous-mix bread containing NFDM (high heat) in amounts from 2-6% of the flour weight, through the incorporation of hydroxylated phosphatide, 0.1% to 1.0% and carrageenan extract of 0.01% to 0.15% of the flour weight.
Fan, U.S. Pat. No. 4,395,426, discloses a dry mix for preparing bread without a kneading step, which contains in addition to other ingredients about 0.5 to 1.5 parts by weight per 100 parts of flour of a glycol alginate and about 2 parts to 10 parts by weight per 100 parts flour of a vegetable gum selected from karaya gum, guar gum, xanthan gum, high viscosity carrageenan gum and mixtures thereof and additionally 1 part to 10 parts of "high heat" non-fat dry milk solids (NFDM).
Dotsenko et als., Pishchevaya Primyshlennost, 1, 32-33 (1987) using NFDM in amounts from 10-15% based on the wheat flour weight, together with monoglyceride esters of diacetyl tataric acid and the multi-enzyme complex MFK-KhP to hydrolyze the NFDM, showed improved rheological properties and binding capacities for the resulting doughs. There were no descriptions of bread products made from these doughs.
Rudel, U.S. Pat. No. 5,178,894 discloses a composition for preparing a bread product containing a wheat flour having a protein content between 10% and 17% by weight and about 24% to 48% based upon the flour weight of "high heat" NFDM and optionally one or more vegetable gums which reverses the negative effect of "high heat" NFDM on loaf volume when employed in amounts greater than 5% based upon the flour weight.
Whey, the water soluble fraction remaining after cheese processing is used in a dried form alone or more frequently in combination with soy flour as a replacement for "high heat" NFDM at levels of about 1% to 4% based upon flour weight. This soy flour/whey blend is being generally adopted by bakers for bread processing due to its lower cost compared to "high heat" NFDM. The whey product used in the blend contains 11% protein (lactalbumen and lactglobulin) and 74% lactose. In the case of the soy flour/whey blend, the soy flour provides additional protein to mimic the levels provided by "high heat" NFDM and also dilutes the lactose to the level of NFDM. This makes it easier to substitute the soy flour/whey blend for NFDM on a weight-for-weight basis. Whey used alone changes the absorption characteristics of the flour even at the levels of 4% based upon flour weight.
Whey protein concentrates have been used to upgrade the nutritional value of bread-like baked goods. Hansen, U.S. Pat. No. 3,561,974, describes the use of a whey concentrate (84% protein on a weight basis) to make a protein enriched bread product. Even though a wheat flour of high gluten content (about 20%) is used, the large dilution of the flour with the whey concentrate (about 67% based on flour weight) produces a weakened dough which is more difficult to machine, is intolerant of "floor time", evidences little or no "oven spring" and requires a longer baking time and hotter ovens than generally employed in bread manufacture because of the higher water content of the dough.
Before the process of staling was understood as it is today, the dryness associated with staled crumb of baked goods led to the use of hydrocolloidal vegetable gums as humectants or moisturizers. These agents take up and hold water in amounts many times their own weight. As an example, the uptake of water by alginates is 26 cc/g in contrast to 1 cc/g for gluten and 0.4 cc/g for undamaged starch. It should be emphasized that these agents are not to be considered anti-stalants, even though the above-cited Andt, U.S. Pat. No. 3,271,164, defines the mixture of karaya and algins and/or carrageenans described as "an additive to retard staling" because loaves treated with 0.5% of the additive showed a greater softness initially and after 96 hours when compared to control loaves. However, the rate of firming used as the index of staling was similar in both groups.
Others claiming improvements in keeping qualities from hydrocolloidal vegetable gums because of moisture retention and softness include: Curtner, U.S. Pat. No. 1,534,783, Epstein, U.S. Pat. No. 1,964,940, and Ament, U.S. Pat. No. 2,158,392. Fiske, U.S. Pat. No. 1,657,116, describes a composition of gum tragacanth, 3.0%, and iodic acid, 0.0175%, based upon 100 lb of bread flour mixture as a bread volume enhancer. Similarly, Dubois, U.S. Pat. No. 3,219,455, describes a bread additive comprising about 20-30 parts vital gluten, 3-5 parts hydrophilic colloid (carboxymethylcellulose) and 0.01 to 0.025 parts of an oxidizing agent (potassium bromate) based upon 1,000 parts of bread flour, which has the property of increasing bread volume and compressibility of breads made from said flours.
There are no reports on "low heat" NFDM (NFDM which has not been heat treated to denature whey protein) showing beneficial effects either from its use in the process of bread making or on the baked products resulting from such processes.